QGroupBox already has a border line, unless you use some style that hides them. Instead of using QWidget, use a QFrame instead.

Thanks , I used it, and QFrame is liked me. But I want to add line to QWidget or GroupBox.
I learned how to add border. But When I use border for one widget, it changes all components which they placed on this widget.
Thanks for helps

I don’t understand your requirements. Why can’t you use QFrame instead of QWidget? It’s whole purpose is being a QWidget with a border. And what is wrong with QGroupBox as-is, as it already has a border?

Could you show us the code you are currently using?

Thanks sir, I solved.